The rapid, high increase in production costs and prices of mineral fertilizers leads to a reduction in their use by farmers, while fertilizer manufacturers consider the use of alternative raw materials and reducing the energy consumption of fertilizer production processes. Given these circumstances, special attention is warranted for suspension fertilizers. The manufacturing of suspension fertilizers is simplified and less energy intensive in comparison with solid fertilizers. This is achieved by omitting certain production stages such as granulation, drying, sifting, which usually contribute to more than half of the production costs. This paper presents the production procedure of suspension fertilizers tailored for cabbage cultivation, utilizing alternative raw materials such as sewage sludge ash and poultry litter ash. The final products are thoroughly characterized. The obtained fertilizers were rich in main nutrients (ranging from 23.38% to 30.60% NPK) as along with secondary nutrients and micronutrients. Moreover, they adhere to the stipulated standards concerning heavy metal content as outlined in the European Fertilizer Regulation. A distribution analysis has showed that suspension fertilizers contain nutrients in both liquid and solid phases. This arrangement facilitates their easy availability for plants and subsequent release upon dissolution in soil conditions. To assess process consistency, the production of the most promising fertilizer was upscaled. A preliminary technological and economic analysis was also conducted. The method of producing suspension fertilizers using alternative raw materials is a simple waste management solution offering nutrient recycling with the principles of circular economy. This approach not only encourages nutrient recycling but also curtails reliance on imported raw materials.

The paper presents an application of Life Cycle Assessment (LCA) method for the environmental evaluation of the technologies for the fertilizers production. LCA has been used because it enables the most comprehensive identifi cation, documentation and quantifi cation of the potential impacts on the environment and the evaluation and comparison of all signifi cant environmental aspects. The main objective of the study was to assess and compare two technologies for the production of phosphorus (P) fertilizers coming from primary and secondary sources. In order to calculate the potential environmental impact the IMPACT 2002+ method was used. The fi rst part of the LCA included an inventory of all the materials used and emissions released by the system under investigation. In the following step, the inventory data were analyzed and aggregated in order to calculate one index representing the total environmental burden. In the scenario 1, fertilizers were produced with use of an integrated technology for the phosphorus recovery from sewage sludge ash (SSA) and P fertilizer production. Samples of SSA collected from two Polish mono-incineration plants were evaluated (Scenario 1a and Scenario 1b). In the scenario 2, P-based fertilizer (reference fertilizer – triple superphosphate) was produced from primary sources – phosphate rock.

The results of the LCA showed that both processes contribute to a potential environmental impact. The overall results showed that the production process of P-based fertilizer aff ects the environment primarily through the use of the P raw materials. The specifi c results showed that the highest impact on the environment was obtained for the Scenario 2 (1.94899 Pt). Scenario 1a and 1b showed the environmental benefi ts associated with the avoiding of SSA storage and its emissions, reaching -1.3475 Pt and -3.82062 Pt, respectively. Comparing results of LCA of P-based fertilizer production from diff erent waste streams, it was indicated that the better environmental performance was achieved in the scenario 1b, in which SSA had the higher content of P (52.5%) in the precipitate. In this case the lower amount of the energy and materials, including phosphoric acid, was needed for the production of fertilizer, calculated as 1 Mg P2O5. The results of the LCA may play a strategic role for the decision-makers in the aspect of searching and selection of the production and recovery technologies. By the environmental evaluation of diff erent alternatives of P-based fertilizers it is possible to recognize and implement the most sustainable solutions.